What If There Is Black Mold in Walls?

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Molds are an important part of the natural world, helping decompose organic matter such as fallen leaves. Molds reproduce by releasing spores into the air, which then fall on pet fur, clothes and shopping bags, where they can be carried indoors. Mold requires nutrients and moisture to grow, which is why it appears in damp areas. Black mold, also called Stachybotrys chartarum or Stachybotrys atra, is one of several types of mold that can grow in walls.


According to the Centers for Disease Control and Prevention, black mold can grow on media that provide low levels of nitrogen and high levels of cellulose. These include dry wall or gypsum board, the materials commonly used to cover interior wall studwork; the paper that covers wall insulation; and wallpaper products. You can identify a black mold problem by sight, due to its characteristic black-green coloring. Other molds are greenish-gray and might grow in the same locations as black mold. Black mold has a musty, earthy smell, and some people identify the smell of urine with it.


Certain molds can produce organic compounds that are toxic to humans when inhaled, called mycotoxins, reports the Environmental Protection Agency. Research published in the March 1985 Journal of Applied and Environmental Microbiology found that black mold produces the mycotoxin macrocyclic trichothenes, which is cytotoxic, or toxic to cells. This mycotoxin is associated with illnesses in sheep and horses that have eaten black mold growing in hay, resulting in rashes and respiratory problems.

Effects on Humans

Black mold in the walls is not benign. The CDC states that black mold usually causes allergy-like symptoms, including sneezing, runny nose and watery eyes. People with respiratory problems such as asthma, or those with weakened immune systems might experience a greater risk of infections from exposure to any type of mold.

The Cleveland Clinic notes that more serious illnesses have been associated with black mold but their causality has not been proven through research. These include sleep disorders, memory loss, sudden infant death syndrome and bleeding lungs in infants.


Although any mold growth in walls should be eradicated, in general, the greater the degree of mold infestation, the greater the risk of health problems. The State of Missouri Department of Health and Senior Services recommends wearing protective gear when cleaning mold infestations, including an N-95 respirator available at hardware stores, household cleaning gloves and eye goggles.

Remove black mold by scrubbing with detergent and water. If sewage or floodwater has caused mold growth, disinfect the area with a mixture of one part bleach to 10 parts water. Absorbent items such as carpet and dry wall might not come clean and may need to be discarded. If the mold problem is severe, contact a professional for assistance.


The best prevention for black mold is reduction of moisture in your home, particularly in or near walls. Ensure your roof, exterior walls, doors and windows are watertight. Check for leaking water spigots and pipes outside, under sinks, and behind toilets, hot water tanks and washing machines. Clean spills or leaks immediately to prevent mold growth.